A thiadiazoleamide derivative or a salt thereof expressed by the following Formula 1: ##STR1## wherein each of R.sub.1 and R.sub.2 represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a lower alkylamino group or an alkenyloxy group; wherein when either R.sub.1 or R.sub.2 is a hydrogen atom, the other is not a hydrogen atom; R.sub.3 represents a lower alkyl group, an aryl group, a pyridyl group or --N(R.sub.4)R.sub.5, wherein R.sub.4 and R.sub.5 represent lower alkyl groups or together represent a saturated heterocyclic ring having 4-8 members; wherein when R.sub.1 or R.sub.2 is a lower alkoxy group, R.sub.3 is --N(R.sub.4)R.sub.5 or a pyridyl group; and n represents an integer of 1-3. The derivatives have anti-ulcer effect to be available for preventing or curing ulcers in mammals.